Carbine VS. Mid-length

[A 7.62 Exodus]

I'm finally starting my AR build process, and I have a question for the AR vets. Do you prefer carbine length uppers or mid-length uppers? Also, why?

Thanks for the help guys!

EDIT: I forgot to add, I'm leaning towards a piston driven system. If that makes a difference.

 

[Mgderf]

What are you going to use it for?

 

[abnk]

Assuming a 16" barrel from the same manufacturer, a mid-length should run smoother in theory. In practice, I cannot really tell a difference. Others might. Also, if sight radius and mounting a bayonet are deciding factors for you, mid-length may be what you want.

For all practical reasons, I think you'll be fine with either.

 

[wsenefeld]

In theory, carbine will be more reliable, but harder on your parts. Most people combat this with a heavier buffer. If you plan on running this for a long while without cleaning or using this as an shtf rifle, I'd go with a carbine length.

If you want a softer shooting rifle or if you plan on suppressing it down the road, definitely get the midlength.

 

[A 7.62 Exodus]

What are you going to use it for?

General target/shtf rifle

 

[Bfish]

I think either gas system will serve you fine, but if I were to have a choice between the two I'd go with a mid-length. I have them and they work great.

 

[seedubs1]

Depends on barrel length. Look up info on "cork time." Educate yourself.

 

[mkbar80]

Assuming you go with a traditional front sight gas block, the rail is typically only 7" on a carbine and its usually 9" on a middle. The midlength system will have more room for light, vertical fore grip, etc. That may, or may not, be important to you...but I'm a large frame guy with long arms. The extra 2" makes a big difference in a comfortable grip on the rifle...at least to me.

Another option is a carbine with a low profile gas block, and a longer free float tube over it.

I'm not sure a piston gets you anything more unless you shoot really high volumes or you're shooting suppressed.


My 2 cents

 

[Fargo]

In theory, carbine will be more reliable, but harder on your parts. Most people combat this with a heavier buffer. If you plan on running this for a long while without cleaning or using this as an shtf rifle, I'd go with a carbine length.

If you want a softer shooting rifle or if you plan on suppressing it down the road, definitely get the midlength.

I'm curious why a carbine would be more reliable? The shorter gas system has a much rougher curve and I would think that a midlength gas system would be easier to run as it has longer pressure curve.

 

[wsenefeld]

I'm curious why a carbine would be more reliable? The shorter gas system has a much rougher curve and I would think that a midlength gas system would be easier to run as it has longer pressure curve.

The carbine length gas system was engineered for a 14.5" barrel. By design, it will be over-gassed on a 16" barrel. On the coldest winter day, try run weak, steel cased tulammo through a rifle that has gone 10,000+ rounds without a cleaning and you'll see the merit in a carbine length gas system.

Obviously that's not a common scenario but in my longevity tests, the carbines run longer while dirty as opposed to the midlengths.

 

[abnk]

Which barrel last longer in your longevity tests?

 

[maxmayhem]

carbine in my experience a little more reliable in all my experiences (though a little bit more recoil)...i have two spikes mid-lengths that have never ever had a reliability problem and two carbines (as well as two pistol systems) .....i like both carbines and midlength systems..i usually put scopes on my mid length rifles and red dot sights on my carbines. There are many things you can do with buffers and springs to mitigate recoil and improve reliability...i also have a new lothar walther midlenth 223 wylde barrel that i am itching to try out but waiting on a couple parts in the mail to finish the upper build....recoil is nothing on an ar 15 but my 10 year old girls and 15 year old complain about it a little on certain guns

 

[wsenefeld]

Which barrel last longer in your longevity tests?

Between my dad and myself, we've tested 4 barrels. Only the premium barrels were tested on how long the rifle would go without a cleaning. The groups on the premiums really started to open up after 7,200 rounds. The other barrels we've tested to see how long they'd last overall. When starting the test, we contacted Ballistic Advantage to see how long their melonite barrels were expected to last. At the time we didn't know much about melonite so they explained it to us and said that if we ever shot out one of their melonite barrels, they'd replace it for free if we sent them the shot out barrel with an estimated round count.

Carbine/midlength premium from PSA 7k-8k rounds
Carbine CHF from PSA 18k-19k rounds
Carbine melonite from Ballistic Advantage 27k+

 

[flatlander]

BCM Filthy 14 ??
I trust Pat. He has more data on what works than anybody I've run across. He runs mid length exclusively.

Bob

 

[A 7.62 Exodus]

BCM Filthy 14 ??
I trust Pat. He has more data on what works than anybody I've run across. He runs mid length exclusively.

Bob

Wait...so they put 40k+ rounds through a mid-length system without a single cleaning? Or am I missing something?

 

[Cerberus]

I've ran everything between 14.5-20 inches. I like the midlength.

 

[AmmoManAaron]

Wait...so they put 40k+ rounds through a mid-length system without a single cleaning?

Yep, with a good build and quality ammo you will wear out the barrel before the rifle needs cleaned. What more can you ask for? The modern AR-15 is truly a wonder. For a short rifle, I favor the mid-length gas system and then run only good quality ammo (no weak, dirty, foreign steel cased crap). It is amazing how often that a reliability or accuracy problem can be traced back to sub-standard ammo. FWIW, I cut the group size of my SKS in half just by using normal handloads (no match bullets or case prep techniques required). The bottom line is that if you care about accuracy and/or reliability, the answer usually lies in quality ammo no matter what firearm you are using.

 

[rhino]

The big key to reliability for any AR is lubrication. Dirty and wet will run longer than clean and dry.

The EAG crew keeps their rifles running because they're always lubed. In my own experience, I've seen the same thing. I haven't cleaned my house gun (a 16" pencil barreled Double Star upper with a carbine gas system and a Bushmaster lower from an AK Shorty) for close to 10 years, but it always works because I keep it lubed. Recently it also sits for months (and sometimes over a year) without being fired because I don't have time to shoot much. It has always worked 100% every time I've pulled it out to fire it.

I would not expect much difference in terms of reliability from a mid-length gas system.

 

[jonny4523]

I'm 100% midlength all the way, every rifle. Both are going to be reliable when assembled and lubed correctly. Midlength has a softer impulse and is easier on parts. With either gas system, you can go with a low profile gas block and stretch your sight radius out to the end of the barrel. Or just get an Aimpoint / EO Tech and be done with it. To Joey's (Rhino) point, lubrication is key. I only clean rifles once a year. I've NEVER had an issue with them. But I keep them well lubed.

Just curious, why are you leaning towards for piston system? I can think of so many reasons to stick with the DI system that a piston system would never even enter my mind (reliability well proven, parts are plentiful, reliability is proven WAY better then piston systems with exception of an actually HK416).

If you ever want to see how systems work through high duration, just ask a rental range that shoots 400,000 rounds each MONTH.

AR endurance findings, at a rental range - The Firearm Blog

 

[Mgderf]

If you ever want to see how systems work through high duration, just ask a rental range that shoots 400,000 rounds each MONTH.

AR endurance findings, at a rental range - The Firearm Blog

Now THAT'S high volume!
I teach classes at Applied Ballistics in Lafayette, and I've also done work behind the scenes in the traps area and above the range around the air handling systems.
I would love to get a look at the working side of THAT range.
It would be fascinating to the see.

That's also a HUGE pile of brass each month.